A last-minute deluge of health insurance sign-ups came from states where political leaders have opposed the Obama administration’s health-care law, according to federal figures released Thursday.

In March and April, the number of people enrolling in plans more than doubled in the 36 states that chose not to set up their own marketplaces, the figures show. Most of these states deferred to the federal marketplace, HealthCare.gov, in a show of resistance to the program.

Nevertheless, many residents of these states rushed to sign up just before this year’s deadline. In Texas and Florida, which have fiercely resisted the Affordable Care Act, nearly 1 million people enrolled between March 1 and April 19. Similar increases took place in Georgia and North Carolina.

An additional 4.8 million people have obtained health coverage through Medicaid, which was expanded under the act, and the Children’s Health Insurance Program.

Myriad questions remain, including whether enough healthy people enrolled in each state to stave off a premium increase, and how many of those who signed up actually paid their first month’s bill — a step that is necessary to ensure that they are covered.

But Democrats immediately seized on the report as evidence that people are seeking to benefit from the law despite Republican attacks.

“The final enrollment report proves that the [Affordable Care Act] is a historic success,” Rep. Henry A. Waxman (Calif.) said in a statement shortly after the numbers were released. “The simple fact is this law is doing an enormous amount of good for the American people.”

The figures were included in a widely anticipated report that offered the first detailed look at the health-care law’s inaugural enrollment period, which got off to a bumpy start on Oct. 1 but ended with the Obama administration exceeding its target by enrolling more than 8 million in the program.

The numbers indicate a high demand for the insurance plans, even in states where political resistance was strongest. In Florida, for instance, where Republican Gov. Rick Scott (R) did not set up a state exchange or expand Medicaid, nearly 40 percent of the eligible population has enrolled, according to a Washington Post analysis of the newly released data.

Even as Republicans have continued to target Democrats who voted for the Affordable Care Act in competitive races, recent polling suggests that Americans, although not enthusiastic about the law, are not eager to repeal it.

In a recent Kaiser Family Foundation poll, 58 percent of those surveyed said Congress should “work to improve the law,” while 35 percent want lawmakers to “work to repeal the law and replace it with something else.”

It also for the first time provided a look at the racial and ethnic breakdown of those signing up for private coverage on the federal marketplace. It found that enrollment was lower than hoped among Hispanics and whites but stronger than expected among blacks and Asians.

The meaningfulness of the data is limited, however, because nearly a third of enrollees did not report their ethnicity, another optional question on the insurance application.

In a teleconference with reporters Thursday, officials acknowledged that Hispanic enrollment was a weak spot. They blamed the numbers on a lack of familiarity among Latinos about the concept of health insurance and a skittishness on the part of people whose families have a mix of legal and illegal immigrants. Legal residents are permitted to receive benefits under the health-care law, while unlawful residents are not.

The progress in enrolling African Americans and Latinos is “an important first step forward in addressing disparities and access to coverage,” Mayra Alvarez, associate director of the Office of Minority Health in the Department of Health and Human Services, told reporters. But, she added, “we recognize there is more work to do.”

About 28 percent of those who enrolled were in the age range of 18 to 34 — a key demographic to keeping the legislation on safe financial footing. And about 54 percent were women.

The report provided a snapshot of how different states fared in coaxing people to enroll.

Collectively, the 14 states, as well as the District, that have their own marketplaces did a slightly better job than the states relying on the federal marketplace, signing up one-third of those who are eligible to buy marketplace coverage.

But that is only because California fared exceedingly well. More than 1.4 million Californians selected health plans by the end of the enrollment period. The state, which has its own marketplace and spent millions in state and federal money to promote the health-care law, enrolled 43 percent of its eligible population.

Without that high number, the state exchanges would have had the same performance as the federal-marketplace states, which did not receive the millions of dollars for outreach that went to states that set up their own.

The poorest outcomes among states that set up marketplaces were in Hawaii, Maryland, Minnesota and Nevada, which signed up less than 20 percent of their potential consumers. All four states have struggled with major technical difficulties. Last week, Oregon abandoned its marketplace and announced that it will rely on the federal exchange.

Among the states that use the federal marketplace, Florida, Idaho and Michigan had the best performances, with just less than 40 percent signed up. Georgia, Maine and North Carolina also had at least 30 percent signed up.

The poorest performances in federal-marketplace states were in Iowa, North Dakota, South Dakota and Wyoming, which all had 15 percent or fewer sign-ups.

Jason Millman contributed to this report.

Sandhya Somashekhar is the social change reporter for the Washington Post.

Dan Keating analyzes data for projects, stories, graphics and interactives. He was part of a team that won a Pulitzer at The Miami Herald for exposing vote fraud, and a team that was a Pulitzer finalist the year before for uncovering police fraud.

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